Replaced a 40" Sony tube set with a new flat 46.
Got two shelf brackets from Home Depot, model 14825, painted them black:
Got two pieces of angle aluminum, 1" x 1" x 1/8" thick. Bolted the aluminum to the short sides of the bracket to make it taller. Drilled holes in the aluminum to line up with the VESA holes. Screwed the horizontal part of the bracket down to the TV shelf.
This worked because the mount did not have to come in front of the TV at all and I could screw down to the surface. An alternate would be to get a couple of pieces of 1x2 or 1x3 oak, figure out how much forward they need to come to keep the TV up, paint them black and mount the shelf brackets to them.
This sounds simple but took a couple of hours at least. That means you don't get paid for your time or it's a $250 mount. But the idea might apply.